The tempo of disease progression following vertical HIV-1 infection is highly variable. As a group, however, vertically-infected children experience more rapid disease progression than children infected at an older age or adult (1,2); over 80%of vertically-infected children manifest HIV-1 related symptoms or CD4 T cell depletion by 2 years of age. In a study of 200 vertically-infected Italian infants followed from birth(1), the median age of onset of any HIV-1 related sign or symptom was 5.2 months (range 0.03-56 months);the probability of remaining asymptomatic was 19% at 12 months and 6.1 % at five years.